Counting and Summing on Multiple Criteria

Many of you will have wanted to use the COUNTIF and SUMIF functions on multiple columns but will have been annoyed about the necessity to introduce very long formulas or additional concatenation columns. This excellent hack allows you to perform COUNTIFs or SUMIFs on multiple columns using the SUMPRODUCT function. Credit to Charley Kyd over at ExcelUser for explaining this one:

SUMPRODUCT hack at ExcelUser